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Concepts Of Physics MCQ Edition [Volume 2]PhysicsThe Nucleus

A sample containing radioactive ¹³¹ I with a half-life of 8.0 days has an initial activity of 20 Ci at t = 0 . Find the decay constant of the sample at t = 4.0 days .

Options

  1. A2.0 10⁻⁶ s ⁻¹
  2. B0.69 10⁻⁶ s ⁻¹
  3. C1.0 10⁻⁶ s ⁻¹
  4. D1.4 10⁻⁶ s ⁻¹

Correct answer

C. 1.0 10⁻⁶ s ⁻¹

Step-by-step solution

The decay constant of a radioactive substance is a characteristic property of the nucleus and is independent of time and the amount of substance present. = 2 T_ 1/2 Given T_ 1/2 = 8.0 days = 8.0 24 60 60 s = 691200 s . = 0.693 691200 s ⁻¹ 1.0 10⁻⁶ s ⁻¹ .

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